The elderly has the physiological characteristics of insufficient essence and qi, declining original qi, and overall deficiency of the four channels and five zang organs, as well as the pathological characteristics of deficiency in the root and excess at the tip, the deficiency-excess complexity, and lingering pathogenic factors due to deficient healthy qi. The kidney, mingmen and triple jiao are physiologically interrelated and complement each other in function. Together with the five zang organs and six fu organs, they play the role of qi transformation as a whole. The deficiency of kidney essence and the decline of mingmen fire are the root causes of age-related debility, while the failure of qi transformation of the triple jiao is the key for transformation between deficiency and excess patterns. From the perspective of “kidney- mingmen-triple jiao qi transformation”, we analyze the TCM pathogenesis and symptoms of debility. Specifically, as the kidney fails to store essence, kidney deficiency may occur; as the kidney is not in charge of the external, pathogenic factors tend to invade the body; when the kidney fails to produce marrow, the spirit may not gather; simultaneously, the triple jiao fails to support qi transformation normally. As a result, a deficiency pattern tends to be complicated with an excess one with lingering pathogenic factors. Such an interpretation may contribute to the deep understanding of the linkage of “essence-qispirit- physique” in age-related debility and the establishment of a correlative dynamic pathogenesis for the condition. [ABSTRACT FROM AUTHOR]